1. Field of the Invention
This invention relates to polymer secondary batteries having a high rate of appearance of capacity and excellent cycle characteristics, and methods of making the same.
2. Description of the Prior Art
In the positive and negative electrodes of conventional secondary batteries, an electrically conducting additive such as carbon is used together with an electrode active material in order to enhance its electrical conductivity. FIG. 4 is a schematic view showing the structure of such an electrode. An electrically conducting additive 53 is dispersed in a film of an electrode active material 52 which is formed on a current collector 51.
However, the use of an organic compound polymer as an electrode active material involves various problems. They include, for example, low efficiency in the utilization of the active material, a low rate of appearance of battery capacity, and the inability to use a substance having low electronic conductivity as an active material. According to investigations made by the present inventors, organic compound polymers generally have poor electronic conductivity when used as active materials, so that the oxidation-reduction reactions do not proceed rapidly. If it is tried to enhance electrical conductivity by adding an electrically conducting additive in large amounts, the rate of appearance of capacity is reduced owing to a limited amount of the active material. Moreover, it has been found that the mere addition of an electrically conducting additive to an electrode active material fails to impart sufficient electrical conductivity thereto because the area of contact between the carbon and the active material is limited to result in low bond strength.
Meanwhile, it is described in Japanese Patent Laid-Open Nos. 74051/' 91 and 290852/' 93 that polypyrrole is formed on a carbon electrode by electrolytic polymerization. However, these patents have the disadvantage that, since polypyrrole is formed on a mass of carbon shaped into an electrode, the active material cannot be secured in such an amount as to give a sufficient capacity.